(1) Field of the Invention
The invention relates to an electroless gold plating solution, particularly a solution capable of plating exactly onto predetermined parts on the workpiece.
(2) Description of the Prior Art
An electroless gold plating solution contains a reducing agent, such as boron potassium hydride or boron sodium hydride, which causes gold deposit onto the workpiece, as disclosed, for example, in the Japanese laid open patent No. 52-124428 or No. 55-24914.
Such conventional plating solutions contain a relatively large amount of a reducing agent to assure high deposition rates, which may, however, lead to excessive reduction of gold by which gold deposits onto unwanted parts of the workpiece, for example outside a metalized part. This may result in undesired electrical connections between separate plated parts arranged at a short distance.
The present invention aims at elimination of such problems associated with conventional plating solutions, and provides an electroless gold plating solution from which gold deposits exactly onto desired parts of the workpiece without undesirable spread of the plated area.